Silver recovery from photographic fixer solution at home level.

i wa trying to recover silver from photographic fixer solution using home made electrolysis unit having 12v and 3 ampere DC source, small graphite, and stainless steel dinning plate, plastic container of 25 L size.  But, after 6 hours, i was unable to get  the expected more than 60gm silver. in fact i get nothing at all. Why it went wrong? what is wrong with the anode, cathode, power voltage and amperage, volume of fixer used, NaOH added---?
With regards!!!